Hydraulic arrangements are known in which mechanical pipe break safety valves are applied with which hydraulic cylinders are secured against unintended retraction or extension, in case that one of the connecting lines should break.
The operating principle of these pipe break safety devices consists of the fact that upon a drop in pressure across the valve, a valve slide is forced against a valve seat by a certain spring force so as to seal against any leakage, and thereby a further flow of oil is prevented.
In most hydraulic arrangements, the securing of a chamber of a hydraulic cylinder loaded by pressure is provided in the form of a load holding valve in hydraulic supply lines. However, if additional components are applied, for example, pressure accumulators, that can be used, for example, in hydro-pneumatic spring support systems or load holding systems, it is useful to also provide a pipe break safety valve arrangement in the connecting lines of the chamber of the hydraulic cylinder that is supplied with pressure, since in case of a break of the connecting lines, the hydraulic cylinder could drop abruptly.
U.S. Pat. No. 5,513,491 discloses a hydraulic arrangement for a lifting arrangement of an operating machine in which several hydraulic cylinders, arranged in parallel, can be connected over connecting lines and shut-off valves with several hydro-pneumatic pressure accumulators. Thereby a hydro-pneumatic spring suspension is to be created with which the lifting arrangement can be spring supported and vibrations of the operating machine can be reduced. The disadvantage here is that the connecting lines are not provided with any pipe break safety arrangements so that in the case of a pipe break in any of the connecting lines, the hydraulic cylinder or cylinders could drop abruptly.
A pipe break safety arrangement is applied, for example, in the patent application disclosed by the Japanese patent office in the patent abstract JP 58121305 AA for a pressure holding system of a hydraulic cylinder. This hydraulic circuit arrangement shows a hydraulic cylinder that is connected over a connecting line with a pressure accumulator. When pressures in the chambers of the cylinder change, the pressure accumulator is intended to compensate so that the pressure in the chambers is maintained. In order to provide assurance that the hydraulic cylinder does not drop upon a pipe break or leakage in the supply line to the pressure accumulator, a mechanical pipe break safety arrangement is arranged in the connecting line in the form of a two-pressure valve. Here the disadvantage develops that such mechanical pipe break safety arrangements tend to close when high volume flows are encountered between hydraulic cylinders and pressure accumulators in hydro-pneumatic spring support systems, without the pressure drop associated with an actual pipe break therefore, such a mechanical pipe break safety arrangement is not appropriate as a protection against a pipe break in pressure accumulator lines for a hydro-pneumatic spring support system.
The task underlying the invention is seen in the need to define a hydraulic arrangement of the type defined initially by means of which the aforementioned problems are overcome.